A common orthodontic technique consists in ligating an arch wire to a bracket mounted against a tooth by means of elastomeric or metal ligature. The ligature is stretched around respective undercuts of gingival and occlusal tie wings so as to overlay the arch wire at mesial and distal ends of the bracket. 
The ligating procedure requires carefully stretching an elastomeric ligature or wrapping and twisting a metal ligature around the tie wings utilizing appropriate orthodontic instruments. The complex ligation procedure contributes to lengthy chair-time. The ligatures tend to loosen up in time diminishing the effectiveness of the arch wire correction. The ligatures also trap food particles in areas of the bracket which are difficult to clean and tend to hide infectious bacteria and viruses such as those of hepatitis B or HIV creating an exposure hazard for the clinician. Moreover, sharp metal ligatures can cause discomfort and even tissue irritation that can lead to infection. 
In an effort to overcome the aforesaid disadvantage of ligatures, a number of alternate arch wire securing mechanisms have been proposed such as the one disclosed in  U.S. Pat. Nos. 3,772,787; 4,077,126; 4,197,642; 4,248,588; 4,344,642; 4,419,078; 4,559,412; 4,561,844; 4,634,661; 4,655,708; 4,712,999; and 4,786,242. 
These so-called pre-engaging or self-engaging orthodontic brackets rely on clasping, sliding or clamping mechanisms which lack the ease of access and of operation that most clinicians desire. 
The present invention results from an attempt to devise a self-engaging orthodontic bracket that can be locked and unlocked with ease upon a section of corrective arch wire. 